The invention concerns a pulsator for milking machines, consisting of a housing that positions a control spindle, of a mechanism that is activated by the control spindle and that alternately connects the pulsator outlets to a source of vacuum and to the atmosphere, of operating chambers, one positioned at each end of the control spindle, that move it back and forth, and of a diversion mechanism that alternately connects each operating chamber to the source of vacuum and to the atmosphere.
A pulsator of this type, which operates in a push-pull mode, is known from German OS 2 931 265. It is employed to alternately connect the spaces between two pairs of teat cups in a milking system to a source of vacuum and to the atmosphere. The time during which the space between the teat cups is connected to the source of vacuum is called the suction phase. Its length can be varied by varying the rate of the pulsator.
The known pulsator has an adjustable choke for varying its rate. The choke is positioned in a line that connects two attenuating chambers in the pulsator. Unavoidable manufacturing tolerances can, however, make the control spindle move at a different speed in each direction. The result is a difference in the durations of the vacuum and atmospheric pressure controlled by the two operating chambers, which can be alternately transmitted to the spaces between the two pairs of teat cups. This irregularity on the part of the known pulsators is called wobble. Furthermore, there is a drawback to adjustable chokes in that they clog up very easily because the cross-section that is to be adjusted is, due to the low capacities of the operating chambers, very small.